Lawrence, I've written up a short summary of what you can
expect to find in UCAC-2 at

http://www.projectpluto.com/datasets.htm#UCAC2

how to use it in Guide at

http://www.projectpluto.com/update8.htm#ucac2_display

and how to use it in Charon at

http://www.projectpluto.com/charon.htm#ucac2

As to whether UCAC-2 really improves astrometry: the answer would
appear to be YES, in large letters set in flaming type. I describe
(at the first of the above URLs) a few cases where you might want
to use other catalogs, but I'd expect such cases to be very rare.

Jerry, you mentioned getting GSC-2.2 data via Internet in an
earlier message. You can get USNO data in the same manner, using
"Get A2.0 via Internet" or "Get B1.0 via Internet". These give
B and R magnitudes. If you set Guide up to show V magnitudes
(the default), then it will compute V from those B and R magnitudes;
click on a star, and you'll get data in all three bands. You
can then compute B-V data.

Be warned that such data is generally not at all reliable.
For variable star work, I strongly recommend looking to get
photometric data elsewhere if at all possible; the values specified
in the USNO catalogs are vague indications, nothing more.

-- Bill